X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=Text%2FRead.hs;h=d935ffec419dfff7dda5c8b8d7b4f9e71ef0e218;hb=8a1129a742003ddacb0fa331309434b5e2953cd8;hp=172a4c2ce3f56b5da92466494b00f54ae8b04105;hpb=10de2c656f74562b662c22928be85e1b3ccda796;p=ghc-base.git

diff --git a/Text/Read.hs b/Text/Read.hs
index 172a4c2..d935ffe 100644
--- a/Text/Read.hs
+++ b/Text/Read.hs
@@ -1,4 +1,5 @@
-{-# OPTIONS_GHC -XNoImplicitPrelude #-}
+{-# LANGUAGE CPP, NoImplicitPrelude #-}
+
 -----------------------------------------------------------------------------
 -- |
 -- Module      :  Text.Read
@@ -45,7 +46,10 @@ module Text.Read (
  ) where
 
 #ifdef __GLASGOW_HASKELL__
+import GHC.Base
 import GHC.Read
+import Data.Either
+import Text.ParserCombinators.ReadP as P
 #endif
 #if defined(__GLASGOW_HASKELL__) || defined(__HUGS__)
 import Text.ParserCombinators.ReadPrec
@@ -68,3 +72,30 @@ parens p = optional
     L.Punc ")" <- lexP
     return x
 #endif
+
+#ifdef __GLASGOW_HASKELL__
+------------------------------------------------------------------------
+-- utility functions
+
+-- | equivalent to 'readsPrec' with a precedence of 0.
+reads :: Read a => ReadS a
+reads = readsPrec minPrec
+
+readEither :: Read a => String -> Either String a
+readEither s =
+  case [ x | (x,"") <- readPrec_to_S read' minPrec s ] of
+    [x] -> Right x
+    []  -> Left "Prelude.read: no parse"
+    _   -> Left "Prelude.read: ambiguous parse"
+ where
+  read' =
+    do x <- readPrec
+       lift P.skipSpaces
+       return x
+
+-- | The 'read' function reads input from a string, which must be
+-- completely consumed by the input process.
+read :: Read a => String -> a
+read s = either error id (readEither s)
+#endif
+